Venezuela's jailed protest leader, Leopoldo López, has urged his supporters to continue their struggle as army tanks, helicopters and paratrooper regiments attempted to restore order after more than a week of clashes that have led to at least eight deaths and 137 wounded.

In a note passed to his wife during a prison visit and then rapidly spread across social networks, the opposition figure said the demonstrations should go on."I'm fine, I ask you not to give up, I won't," López wrote from a Caracas prison. "To the youth, to the protesters, I ask you to stay firm against violence, and to stay organised and disciplined. This is everyone's struggle."

The message is likely to give impetus to a movement described by the government as a US-backed coup attempt to seize power in the oil-rich nation. It will also add to the leadership credentials of a politician who, until a week ago, was little known in the wider world. The 42-year-old is a political blue-blood from one of the most powerful families in Venezuela. Several ancestors have held cabinet posts, including a great, great grandfather who was a former president.

In character, if not in politics or background, López has been compared to the late president Hugo Chávez, who could also be uncompromising to the point of recklessness – much to the frustration of his ostensible allies.

"For opposition parties, López draws ire second only to Chavez … the only difference between the two is that López is a lot better looking," Mary Ponte – a prominent figure in the Primero Justicia Party – was cited as saying in a 2009 US embassy cable released by WikiLeaks.

The US embassy described López as necessary, but troublesome. Under the heading "The López Problem", diplomats acknowledged that many in the opposition did not trust his motives, even though they need his support to reach out to the public. "He is often described as arrogant, vindictive, and power-hungry – but party officials also concede his popularity, charisma and talent as an organiser," it says.

López attended one of Caracas's elite schools, Los Arcos for a couple years and later studied at the Kennedy school of government in Harvard University.

A college friend, Rob Gluck said López established an activist group called Active Students Helping the Earth Survive. According to Gluck, he was anything but the rightwing figure that he is often portrayed as by the Venezuelan government. "Calling Leo rightwing is like calling Maya Angelou a racist. It is bizarre. It is the ultimate Orwellian exercise in doublespeak."

Friends say his patriotism is evidenced by the tattoo of Venezuela on his ankle. But they also described López – who has often taken to Twitter to taunt President Nicolás Maduro – at one stage asking him "don't you have the guts to arrest me?" – as extremely competitive."Leopoldo was always very competitive. Going out at night with him was always quite hard because he was always very popular with girls", said Alberto Wallis, who has known him since his teens.

At the age of 29, López was elected mayor of the Chacao municipality, the richest in Latin America. He initially won plaudits for revamping the public health system and building new public spaces, but was later charged with embezzlement and stripped of the right to run for office – an accusation that López denies as politically motivated.

López is now married to Lilian Tintori, who used to host a TV program about extreme sports. The couple are sometimes mocked as Barbie and Ken for their perfect looks, but their tearful public parting before López handed himself over to the national guard has proved a powerful image on social networks.

He has long had a rivalry as well as a friendship with the ostensible head of the opposition, Henrique Capriles, who was mayor of a neighbouring district in Caracas. During the failed 2002 coup that saw Chávez ousted for three days, they jointly arrested the minister of interior affairs, earning them the nickname "Batman and Robin".

López has now proved himself the more dynamic of the duo. While Capriles accepted last December's municipal election loss with a handshake with Maduro, López launched a radical movement named "La Salida" (The Exit) which aims to unseat the president through protests. It was his call for street demonstrations that began the current cycle of unrest.

López's detention has made him a figurehead of the opposition movement, but whether that will lead them to power or more futile unrest – as in 2002 – is debated. Critics say his radical stance has simply polarised society, which will be to the advantage of the Chavista government, which has a numerical advantage as well as control of the military, the courts, parliament and community militias.

Others, however, say that his confrontational strategy has more chance of success than conciliation in a country that has often been ruled by caudillo strongmen. Hugo Chávez was a little-known army colonel until he led an unsuccessful coup attempt in 1992 that resulted in more than 140 deaths. He was thrown in jail, but seven years later he was president.

A similar outcome is far from certain. Beaten in election after election, the opposition has tried and failed before to use street protest to grab power, but the attempts in 2002 led to injuries and deaths but no long-term change in administration.